COOLING AND FLAME PROTECTION COMPOSITION FOR A DRIVE SYSTEM OF AN ELECTRIC OR HYBRID VEHICLE

Description

[0001] The present invention relates to the field of propulsion systems for electric or hybrid vehicles, and more particularly to their lubrication and / or cooling means. It thus aims to propose a composition provided with at least cooling properties for the power electronics and the battery, and possibly lubrication with respect to the transmission of the propulsion system, and both properties combined with respect to the engine in a propulsion system of an electric or hybrid vehicle. The composition further has ignition resistance properties, which is useful with respect to batteries. In other words, the present invention aims in particular to provide a means of cooling the batteries of electric or hybrid vehicles via a fluid that can cool but also delay and / or prevent the spread of fire.

[0002] The evolution of international standards for the reduction of CO2 emissions, but also for the reduction of energy consumption, is pushing car manufacturers to offer alternative solutions to combustion engines.

[0003] One solution identified by car manufacturers is to replace combustion engines with electric motors. Research into reducing CO2 emissions has therefore led to the development of electric vehicles by several car companies.

[0004] For the purposes of the present invention, the term "electric vehicle" means a vehicle comprising an electric motor as the sole means of propulsion, unlike a hybrid vehicle which comprises a combustion engine and an electric motor as combined means of propulsion.

[0005] For the purposes of the present invention, the term "propulsion system" means a system comprising the mechanical parts necessary for the propulsion of an electric vehicle. The propulsion system thus more particularly encompasses an electric motor comprising the rotor-stator assembly, power electronics (dedicated to speed regulation), a transmission and a battery.

[0006] Generally speaking, it is necessary to implement, in electric or hybrid vehicles, compositions to meet the lubrication and / or cooling constraints of the various parts of the propulsion system mentioned above.

[0007] Depending on the systems, a single composition may play the role of lubrication and cooling, while in other systems there may be both a lubricating composition dedicated to this action with respect to the elements of the propulsion system, as has just been described, and a different cooling composition, in particular for the batteries and power electronics.

[0008] This second alternative is used in particular when hydrocarbon fluids having a boiling point greater than or equal to 50°C, and in particular between 50°C and 350°C, in particular between 60°C and 250°C, and even more particularly between 80°C and 200°C, are used for cooling batteries and power electronics as will be detailed below. Such hydrocarbon fluids do not have lubricating properties.

[0009] A cooling, and possibly lubricating, composition according to the invention, while ensuring the cooling of the battery, guarantees the safety of the batteries.

[0010] According to a particular embodiment, the composition according to the invention plays the dual role of cooling and lubrication.

[0011] Still according to this embodiment, for the electric motor itself, the composition plays both a lubricating and cooling role. For the power electronics, the composition plays a cooling role. The transmission is lubricated by the composition and finally the batteries are cooled by said composition.

[0012] Lubricating compositions, also known as "lubricants", are commonly used in propulsion systems, such as electric motors, primarily for the purpose of reducing friction forces between the various moving metal parts in the motors. They are also effective in preventing premature wear and even damage to these parts, particularly their surfaces.

[0013] To do this, a lubricating composition is classically composed of one or more base oils, to which are generally associated several additives dedicated to stimulating the lubricating performance of the base oils, such as for example friction modifying additives.

[0014] On the other hand, electric propulsion systems generate heat during operation viathe electric motor, power electronics and batteries. Since the amount of heat generated is greater than the amount of heat normally dissipated to the environment, it is necessary to ensure cooling of the motor, power electronics and batteries. Generally, cooling is carried out on several parts of the propulsion system that generate heat and / or parts of said system that are sensitive to heat, in order to avoid reaching dangerous temperatures, and in particular the power electronics and batteries.

[0015] Traditionally, electric motors have been cooled with air or water, possibly combined with glycol. These cooling methods are not optimal, and may even be insufficient with the new developments in the propulsion system of electric and hybrid vehicles.

[0016] Flame retardants are also known which can be used in fluids, including oily ones, particularly for industrial applications.

[0017] However, some virtually non-flammable oils are generally composed of heavy halogens such as polychlorotrifluoroethylenes (PCTFE). Furthermore, some perfluorinated organic fluids of the ether or ketone type are also known as coolants for the propulsion system of electric vehicles.

[0018] These halogenated compounds are very expensive and their use is not preferred for regulatory and environmental reasons. In addition, these halogenated compounds have a high density which adds to the mass of the battery and which would ultimately reduce the vehicle's autonomy.

[0019] Despite the cooling systems known in the field of lubrication of propulsion systems of electric or hybrid vehicles, the risk cannot be completely ruled out of seeing the battery overheat at the level of a cell, which can lead to an explosion and an overall fire of the battery, called the "runaway effect". This is in particular what can be feared in the operation of a Li-ion battery in particular targeted in the context of the present invention.

[0020] The present invention aims precisely to propose a new composition making it possible to satisfy at least the cooling of the elements of the aforementioned propulsion system on the one hand, as well as on the other hand to ensure the safety of the batteries, in particular Lithium-ion (Li-ion) or Nickel-Cadmium (Ni-Cd) batteries, by conferring an ignition resistance property.

[0021] The inventors have discovered that it is possible to ensure at least the cooling function, as well as resistance to ignition for a propulsion system of an electric or hybrid vehicle, by using at least one flame retardant, and more particularly a fluorinated flame retardant of formula (I) as defined below, in particular in a form encapsulated in a cooling composition comprising at least one hydrocarbon fluid having a boiling point of at least 50°C or in a base oil.

[0022] More specifically, the encapsulation of all or part of the retarder of formula (I) makes it possible to control its release into the base oil and therefore to give it non-flammable properties as soon as a runaway effect occurs. It has also been found that the encapsulation of the flame retardant makes it possible to control its release into the environment and to improve its solubilization in the cooling composition.

[0023] The composition thus formed can be placed in direct contact with the propulsion system and cool the engine, the power electronics and the battery by means of this direct contact of said composition on these components, while ensuring increased safety in the event of said battery racing.

[0024] The composition thus in direct contact with these organs provides better cooling than conventional air cooling and indirect water contact. This direct contact allows for better heat dissipation.

[0025] Indeed, air cooling allows direct cooling, but air is a very poor fluid for dissipating heat. Conversely, water is an efficient fluid for cooling but is not compatible with direct contact with the motor, power electronics, and battery.

[0026] Thus, the present invention relates, according to a first of its aspects, to a cooling composition for a propulsion system of an electric or hybrid vehicle, comprising: (i) at least one base oil, or at least one hydrocarbon fluid having a boiling point greater than or equal to 50°C; and (ii) at least one flame retardant corresponding to the formula (I) RF -LR H (I) in which RF is a perfluorinated or partially fluorinated group, in particular comprising from 1 to 22, preferably from 1 to 20, even more preferably from 1 to 16 carbon atoms, RH is a hydrocarbon group, in particular comprising from 1 to 22, preferably from 1 to 20, even more preferably from 1 to 16 carbon atoms, and L is a linker, said flame retardant of formula (I) being at least partially in an encapsulated form; said flame retardant of formula (I) being present in a content of between 0.5% and 40% by weight, relative to the total weight of the composition; said composition being free of water.

[0027] The present invention also relates to the use of at least one flame retardant corresponding to the formula (I) RF -LR H (I) in which RF is a perfluorinated or partially fluorinated group, in particular comprising from 1 to 22, preferably from 1 to 20, even more preferably from 1 to 16 carbon atoms, RH is a hydrocarbon group, in particular comprising from 1 to 22, preferably from 1 to 20, even more preferably from 1 to 16 carbon atoms, and L is a linker, said flame retardant of formula (I) being at least partially in an encapsulated form, in a cooling composition of a propulsion system of an electric or hybrid vehicle, comprising at least one battery, to give it ignition resistance properties.

[0028] More particularly, the cooling composition, thus added, is intended to be placed in direct contact with the batteries of electric vehicles, in particular Li-ion batteries or Ni-Cd batteries, which are in particular immersed or semi-immersed, static or in circulation, in said added cooling composition, or composition according to the invention, or even directly sprayed in the form of a spray, jet or oil mist.

[0029] Document US 2016 / 257886 discloses a flame retardant composition for the battery of an electric vehicle, said composition comprising water, a glycol and a flame retardant encapsulated in high density polyethylene. Preferably, said flame retardant is a bromine compound.

[0030] Fluorinated compounds, and in particular in the form of diblock fluorinated compounds, are described in document WO97 / 21425. However, these fluorinated compounds are described as dispersing agents for controlling the bioavailability and efficacy of lipophilic compounds in emulsions. No application in accordance with the present invention is described or suggested therein.

[0031] A composition according to the invention makes it possible to effectively cool the battery, the power electronics and the motor present in an electric or hybrid vehicle.

[0032] Also, a composition according to the invention makes it possible to delay or prevent thermal runaway, or even the spread of fire in the event of ignition of one of the battery cells.

[0033] The invention also relates to a method for cooling and fireproofing a battery of a propulsion system of an electric or hybrid vehicle comprising at least one step of bringing at least one battery, in particular a Lithium-ion or Nickel-Cadmium battery, into contact with a composition according to the invention.

[0034] Other characteristics, variants and advantages of the implementation of a composition according to the invention will emerge more clearly on reading the description and the figure which follow, given for illustrative and non-limiting purposes of the invention.

[0035] In the context of the present invention, the terms "flame retardant", "fire-safe", "flame retardant", "retardant and / or preventing the spread of fire" or "ignition resistant" may be used interchangeably. All these terms describe compounds having the capacity to make an object safe in the event of an explosion or a fire, in particular following overheating.

[0036] In the rest of the text, the expressions "between ... and ...", "ranging from ... to ..." and "varying from ... to ..." are equivalent and are intended to mean that the limits are included, unless otherwise stated.

[0037] There figure 1 is a schematic representation of an electric or hybrid propulsion system. COMPOSITION

[0038] As indicated previously, a composition according to the invention comprises at least one base oil or fluid base as explained below, and a flame retardant corresponding to formula (I), defined in detail below, said flame retardant being at least partially in an encapsulated form.

[0039] More particularly, a composition according to the invention has a kinematic viscosity, measured at 100°C according to standard ASTM D445, of between 2 and 8 mm 2 < / s, preferably between 3 and 7 mm 2 < / s. Oil of base

[0040] A composition according to the invention may use at least one base oil, in particular a fluid base formed from one or more base oils, having a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, ranging from 1.5 to 8 mm 2 < / s, in particular from 1.5 to 6.1 mm 2 < / s, more particularly from 1.5 to 4.1 mm 2 < / s, even more particularly from 1.5 to 2.1 mm 2 < / s.

[0041] This base oil can be a mixture of several base oils, namely a mixture of 2, 3 or 4 base oils.

[0042] In the remainder of the text, the term "fluid base" will be used to refer to the oil or mixture of base oils, having a kinematic viscosity measured at 100°C according to the ASTM D445 standard ranging from 1.5 to 8 mm 2 < / s.

[0043] The base oil used in a cooling composition according to the invention may be chosen from oils of mineral or synthetic origin belonging to groups I to V according to the classes defined in the API classification (or their equivalents according to the ATIEL classification) and presented in table A below or their mixtures, provided that the oil or mixture of oils has the desired viscosity mentioned above. Table A Saturated content Sulfur content Viscosity index (VI) Group I < 90 % > 0,03 % 80 ≤VI < 120 Mineral oils Group II ≥90 % ≤0,03 % 80 ≤VI < 120 Hydrocracked oils Group III ≥90 % ≤0,03 % ≥120 Hydrocracked or hydroisomerized oils Group IV Polyalphaolefins (PAO) Group V Esters and other bases not included in groups I to IV

[0044] Mineral base oils include all types of base oils obtained by atmospheric and vacuum distillation of crude oil, followed by refining operations such as solvent extraction, de-alphatting, solvent dewaxing, hydrotreating, hydrocracking, hydroisomerization and hydrofinishing.

[0045] Blends of synthetic and mineral oils, which can be bio-sourced, can also be used.

[0046] There is generally no limitation on the use of different base oils to produce the compositions according to the invention, except that they must, in addition to meeting the aforementioned viscosity criterion, have properties, in particular viscosity index, sulfur content or resistance to oxidation, suitable for use in propulsion systems of an electric or hybrid vehicle.

[0047] According to one embodiment, the base oil(s) of a composition according to the invention are hydrocarbon oils, preferably alkanes.

[0048] Still according to this embodiment, the base oil(s) may be chosen from alkanes comprising at least 8 carbon atoms, for example between 8 and 22 carbon atoms, preferably between 15 and 22 carbon atoms. For example, they may be C 8 -C 22 alkanes, preferably C 15 -C 22 .

[0049] The base oils of the compositions according to the invention may also be chosen from synthetic oils, such as certain esters of carboxylic acids and alcohols, from polyalphaolefins (PAO), and from polyalkylene glycols (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

[0050] PAOs used as base oils are, for example, obtained from monomers containing 4 to 32 carbon atoms, for example from octene or decene.

[0051] The weight average molecular mass of PAO can vary quite widely. Preferably, the weight average molecular mass of PAO is less than 600 Da. The weight average molecular mass of PAO can also range from 100 to 600 Da, from 150 to 600 Da, or from 200 to 600 Da.

[0052] For example, the PAOs used in the context of the invention, having a kinematic viscosity, measured at 100°C according to the ASTM D445 standard, ranging from 1.5 to 8 mm 2 < / s are sold commercially by Ineos under the brands Durasyn ® < 162, Durasyn ® < 164, Durasyn ® < 166 and Durasyn ® < 168.

[0053] Esters of carboxylic acids and alcohols are, for example, diesters of formula (II): R a< -C(O)-O-([C(R) 2 ] n -O) s -C(O)-R b< (II) in which: R represent, independently of each other, a hydrogen atom or a linear or branched (C 1 -C 5 )alkyl group, in particular a methyl, ethyl or propyl group, in particular methyl; s is 1, 2, 3, 4, 5 or 6; n is 1, 2 or 3; it being understood that, when s is different from 1, n may be identical or different; and R a< and R b< , identical or different, represent, independently of each other, saturated or unsaturated, linear or branched hydrocarbon groups, having a linear chain of 6 to 18 carbon atoms.

[0054] Preferably, when s and n are identical and equal to 2, at least one of the R groups represents a linear or branched (C 1 -C 5 )alkyl group; and when s is equal to 1 and n is equal to 3, at least one of the R groups linked to the carbon in the beta position of the oxygen atoms of the ester functions represents a hydrogen atom.

[0055] Advantageously, the base oil or oils of the composition according to the invention are chosen from polyalphaolefins (PAO).

[0056] Preferably, a composition according to the invention comprises a fluid base formed from one or more base oils having a kinematic viscosity measured at 100°C according to standard ASTM D445 of between 1.5 and 8 mm 2 < / s.

[0057] In other words, a composition according to the invention may be free of base oil or mixture of base oils not meeting the criterion of kinematic viscosity measured at 100°C according to standard ASTM D445, in particular free of oil or mixture of base oils having a viscosity greater than 9 mm 2 < / s.

[0058] In particular, the base oil may be chosen from alkanes comprising at least 8 carbon atoms, for example between 8 and 22 carbon atoms, preferably between 15 and 22 carbon atoms or from synthetic oils of the carboxylic acid and alcohol ester type, polyalphaolefins (PAO), or polyalkylene glycol (PAG) obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

[0059] It is up to a person skilled in the art to adjust the content of fluid base to be used in a composition according to the invention to achieve the desired viscosity for the composition.

[0060] As indicated above, the fluid base provides the lubricating and cooling potential of the composition according to the invention. In particular, the fluidity of the base ensures good cooling properties when the composition is used in contact with the batteries of a propulsion system of an electric or hybrid vehicle.

[0061] The cooling properties of the composition used are further advantageously increased by the shear applied to the composition at the injection level which brings the fluid to a lower viscosity level than at rest.

[0062] In particular, a composition used according to the invention comprises from 60% to 99.5% by weight, preferably from 70% to 98%, even more preferably from 80% to 98%, advantageously from 90% to 97% by weight of base oil, or mixture of base oils, having a kinematic viscosity measured at 100°C according to the ASTM D445 standard ranging from 1.5 to 8 mm 2 < / s, relative to the total weight of the composition. Hydrocarbon fluid

[0063] The cooling composition of a propulsion system of an electric or hybrid vehicle according to the present invention may comprise at least one hydrocarbon fluid having a boiling point greater than or equal to 50°C.

[0064] According to a particular embodiment of the invention, the hydrocarbon fluid has a boiling point of between 50 and 350°C, in particular between 60 and 250°C, and even more particularly between 80 and 200°C.

[0065] Preferably, the hydrocarbon fluid in accordance with the invention has a carbon content of biological origin greater than or equal to 90% by weight, relative to the total weight of the hydrocarbon oil.

[0066] For the purposes of the present invention, the term "hydrocarbon fluid" means any fluid comprising linear, saturated or unsaturated hydrocarbon molecules, which may also comprise aromatic or cyclic groups, or even heteroatoms.

[0067] Advantageously, the hydrocarbon fluid in accordance with the invention is a hydrocarbon comprising at least 8 carbon atoms, for example between 8 and 22 carbon atoms, preferably between 15 and 22 carbon atoms. For example, it may be a C 8 -C 22 alkane, preferably C 15 -C 22 .

[0068] Advantageously, the hydrocarbon fluid in accordance with the invention is fully saturated. Preferably, the components of the hydrocarbon fluid are chosen from isoparaffins comprising from 12 to 30 carbon atoms, preferably from 13 to 19 carbon atoms, and more preferably from 14 to 18 carbon atoms.

[0069] The cooling composition according to the invention advantageously comprises a weight content of isohexadecane of less than or equal to 50%.

[0070] According to a particular embodiment of the invention, the hydrocarbon fluid comprises alkanes, or linear molecules of saturated hydrocarbons with a non-cyclic chain, in particular comprising between 12 and 30 carbon atoms, in a content of between 80 and 100% by weight, relative to the total weight of the hydrocarbon fluid, or even between 90 and 100% by weight, and for example between 95 and 100% by weight.

[0071] In the context of the present invention, “paraffins” designate hydrocarbons with straight chains (also called “normal paraffins”) or branched chains (also called “isoparaffins”).

[0072] As heteroatoms, in the context of the present invention, mention may in particular be made of nitrogen and oxygen.

[0073] According to a particular embodiment of the invention, the hydrocarbon fluid comprises from 90 to 100% by weight of isoparaffins, a content of normal paraffins ranging from 0 to 10% by weight and a content of carbons of biological origin greater than or equal to 90% by weight relative to the total weight of the hydrocarbon fluid.

[0074] The hydrocarbon fluid advantageously comprises a content greater than or equal to 90% by weight, in particular greater than or equal to 95% by weight, and even more advantageously greater than or equal to 98% by weight of isoparaffins, relative to the total weight of hydrocarbon fluid.

[0075] According to one embodiment of the invention, the isoparaffins present in the hydrocarbon fluid comprise from 12 to 30 carbon atoms, preferably from 13 to 19 carbon atoms and even more preferably from 14 to 18 carbon atoms.

[0076] The hydrocarbon fluid advantageously comprises a normal paraffin content of less than or equal to 10% by weight, preferably less than or equal to 5% and even more preferably less than or equal to 2% by weight, relative to the total weight of the hydrocarbon fluid.

[0077] The isoparaffins are advantageously non-cyclic isoparaffins. Preferably, the hydrocarbon fluid has a mass ratio of isoparaffins to normal paraffins of at least 12:1, preferably at least 15:1 and more preferably at least 20:1. According to an even more particular embodiment, the hydrocarbon fluid does not comprise normal paraffins.

[0078] According to one embodiment, the hydrocarbon fluid preferably comprises a weight content of isoparaffins ranging from 90 to 100% and a content of normal paraffins ranging from 0 to 10%, preferably from 95 to 100% of isoparaffins chosen from alkanes comprising from 12 to 30 carbon atoms, preferably from 12 to 24 carbon atoms, more preferably from 12 to 22 carbon atoms.

[0079] According to a particular embodiment, the hydrocarbon fluid in accordance with the invention comprises a majority, that is to say more than 90% by weight, of molecules having from 14 to 18 carbon atoms, such as isoparaffins.

[0080] According to another embodiment, the hydrocarbon fluid in accordance with the invention comprises from 60 to 95% by weight, preferably from 80 to 98% by weight, of isoparaffins chosen from the group consisting of C15 isoparaffins, C16 isoparaffins, C17 isoparaffins, C18 isoparaffins and mixtures of two or more of them.

[0081] According to one embodiment, the hydrocarbon fluid comprises: isoparaffins having 15 carbon atoms and isoparaffins having 16 carbon atoms in a total amount ranging from 80 to 98% by weight, relative to the total weight of the hydrocarbon fluid, or isoparaffins having 16 carbon atoms, isoparaffins having 17 carbon atoms and isoparaffins having 18 carbon atoms in a total amount ranging from 80 to 98% by weight, relative to the total weight of the hydrocarbon fluid, or isoparaffins having 17 carbon atoms and isoparaffins having 18 carbon atoms in a total amount ranging from 80 to 98% by weight, relative to the total weight of the hydrocarbon fluid.

[0082] According to a preferred embodiment of the invention, the hydrocarbon fluid comprises isoparaffins having 17 carbon atoms and isoparaffins having 18 carbon atoms in a total amount ranging from 80 to 98% by weight, relative to the total weight of the hydrocarbon fluid.

[0083] Examples of preferred hydrocarbon fluids according to the invention are those comprising: from 30 to 70% by weight of C15 isoparaffins and from 30 to 70% by weight of C16 isoparaffins, preferably from 40 to 60% by weight of C15 isoparaffins and from 35 to 55% by weight of C16 isoparaffins, relative to the total weight of the hydrocarbon fluid, from 5 to 25% of C15 isoparaffins, from 30 to 70% of C16 isoparaffins and from 10 to 40% of C17 isoparaffins, preferably from 8 to 15% of C15 isoparaffins, from 40 to 60% of C16 isoparaffins and from 15 to 25% of C17 isoparaffins, relative to the total weight of the hydrocarbon fluid, from 5 to 30% of C17 isoparaffins and 70 to 95% of C18 isoparaffins, preferably 10 to 25% of C17 isoparaffins and 70 to 90% of C18 isoparaffins, relative to the total weight of the hydrocarbon fluid.

[0084] The hydrocarbon fluid preferably comprises a content by weight of naphthenic compounds less than or equal to 3%, preferably less than or equal to 1%, more preferably less than or equal to 0.5% and even more preferably less than or equal to 500 ppm, or even 100 ppm or 50 ppm.

[0085] According to another preferred embodiment, the hydrocarbon fluid comprises a weight content of isoparaffins ranging from 90 to 100%, a weight content of normal paraffins ranging from 0 to 10% and a weight content of naphthenic compounds less than or equal to 1%. Preferably, the hydrocarbon fluid comprises a weight content ranging from 95 to 100% of isoparaffins, from 0 to 5% of normal paraffins and a weight content of naphthenic compounds less than or equal to 0.5%. More preferably, it comprises a weight content ranging from 98% to 100% of isoparaffins, from 0 to 2% of normal paraffins and a weight content of naphthenic compounds less than or equal to 100 ppm.

[0086] The hydrocarbon fluid is advantageously free of aromatic compounds. By example, we mean a content by weight of aromatic compounds less than or equal to 500 ppm, preferably less than or equal to 300 ppm, preferably less than or equal to 100 ppm, more preferably less than or equal to 50 ppm and advantageously less than or equal to 20 ppm measured for example by UV spectrometry.

[0087] The weight content of isoparaffins, normal paraffins, naphthenic compounds and / or aromatics in the hydrocarbon fluid can be determined according to methods well known to those skilled in the art. Mention may be made, by way of non-limiting example, of a method using gas chromatography.

[0088] According to another preferred embodiment, the hydrocarbon fluid comprises a weight content of isoparaffins ranging from 90 to 100%, a weight content of normal paraffins ranging from 0 to 10%, a weight content of naphthenic compounds less than or equal to 1% and a weight content of aromatic compounds less than or equal to 500 ppm. Preferably, the hydrocarbon fluid comprises a weight content ranging from 95 to 100% of isoparaffins, from 0 to 5% of normal paraffins, a weight content of naphthenic compounds less than or equal to 0.5% and a weight content of aromatic compounds less than or equal to 300 ppm, preferably less than 100 ppm, preferably less than 50 ppm and advantageously less than 20 ppm. Preferably also the hydrocarbon fluid comprises a weight content ranging from 95 to 100% of isoparaffins, from 0 to 5% of normal paraffins and a weight content of aromatic compounds less than or equal to 100 ppm.More preferably, it comprises a weight content ranging from 98% to 100% of isoparaffins, from 0 to 2% of normal paraffins, a weight content of naphthenic compounds less than or equal to 100 ppm and a weight content of aromatic compounds less than or equal to 100 ppm.

[0089] The hydrocarbon fluid also preferably has an extremely low weight content of sulfur compounds, typically less than or equal to 5 ppm, preferably less than or equal to 3 ppm and more preferably less than or equal to 0.5 ppm at a level too low to be detected using conventional low-sulfur analyzers.

[0090] The hydrocarbon fluid also preferably has a flash point greater than or equal to 110°C, preferably greater than or equal to 120°C and more preferably greater than or equal to 140°C according to standard EN ISO 2719. A high flash point, typically greater than 110°C, makes it possible, among other things, to overcome safety problems during storage and transport by avoiding excessive flammability of the hydrocarbon fluid.

[0091] The hydrocarbon fluid also preferably has a vapor pressure at 20°C less than or equal to 0.01 kPa.

[0092] According to one embodiment, the hydrocarbon fluid also preferably has a flash point greater than or equal to 110°C according to standard EN ISO 2719 and a vapor pressure at 20°C less than or equal to 0.01kPa. Preferably, the hydrocarbon fluid has a flash point greater than or equal to 120°C and a vapor pressure at 20°C less than or equal to 0.01kPa. And more preferably, it has a flash point greater than or equal to 140°C and a vapor pressure at 20°C less than or equal to 0.01kPa.

[0093] The hydrocarbon fluid has boiling temperatures, flash point and vapor pressure to overcome flammability, odor and volatility issues.

[0094] The hydrocarbon fluid also preferably has a kinematic viscosity at 40°C less than or equal to 5 cSt, preferably less than or equal to 4 cSt and more preferably less than or equal to 3.5 cSt according to standard EN ISO 3104. Process for obtaining the hydrocarbon fluid:

[0095] Such hydrocarbon fluids can be obtained in the following way. The hydrocarbon fluid according to the invention is a hydrocarbon cut which is obtained from the conversion of biomass.

[0096] By "product of biomass conversion" is meant, in the context of the present invention, a hydrocarbon fraction produced from raw materials of biological origin.

[0097] Preferably, the hydrocarbon fraction of biological origin is obtained by a process comprising hydrodeoxygenation (HDO) and isomerization (ISO) steps. The hydrodeoxygenation (HDO) step leads to the decomposition of the structures of the biological esters or triglyceride constituents, to the elimination of oxygenated, phosphorus and sulfur compounds and to the hydrogenation of the olefinic bonds. The product resulting from the hydrodeoxygenation reaction is then isomerized. A fractionation step may preferably follow the hydrodeoxygenation and isomerization steps. Advantageously, the fractions of interest are then subjected to hydrotreatment and then distillation steps in order to obtain the specifications of the desired hydrocarbon fluid according to the invention.

[0098] This HDO / ISO process is carried out on a raw biological feedstock, also called biomass or raw material of biological origin, selected from the group consisting of vegetable oils, animal fats, fish oils and their mixtures. Suitable raw materials of biological origin are, for example, rapeseed oil, canola oil, tall oil, sunflower oil, soybean oil, hemp oil, olive oil, linseed oil, mustard oil, palm oil, peanut oil, castor oil, coconut oil, animal fats such as tallow, recycled edible fats, raw materials from genetic engineering, and biological raw materials produced from microorganisms such as algae and bacteria. Condensation products, esters or other derivatives obtained from raw biological materials can also serve as raw materials.

[0099] Preferably, the raw material of biological origin is an ester or a triglyceride derivative. This material is first subjected to a hydrodeoxygenation (HDO) step to decompose the structure of the constituent esters or triglycerides and to eliminate the oxygenated, phosphorus and sulfur compounds concomitantly with the hydrogenation of the olefinic bonds. This hydrodeoxygenation (HDO) step of the raw material of biological origin is followed by an isomerization of the product thus obtained leading to the branching of the hydrocarbon chain and to an improvement in the properties of the paraffin at low temperatures.

[0100] During the HDO step, hydrogen and the biologically derived raw material are passed through a hydrodeoxygenation catalyst bed simultaneously or countercurrently. During the HDO step, the pressure and temperature are between 20 and 150 bar and between 200 and 500°C respectively. Conventional and known hydrodeoxygenation catalysts are used during this step. Optionally, the biologically derived raw material may be subjected to pre-hydrogenation under mild conditions to avoid secondary reactions of the double bonds before the HDO step. After the hydrodeoxygenation step, the reaction product is subjected to an isomerization step (ISO) where hydrogen and the product, and possibly a mixture of n-paraffins, are passed through isomerization catalyst beds simultaneously or countercurrently.During the ISO stage, the pressure and temperature are between 20 and 150 bars and between 200 and 500°C respectively. Conventional and known isomerization catalysts are used during this stage.

[0101] Additional secondary processes may also be implemented (such as intermediate mixing, trapping or other such processes).

[0102] The product from the HDO / ISO steps can optionally be fractionated to obtain the cuts of interest.

[0103] Various HDO / ISO processes are described in the literature. Application WO2014 / 033762 describes a process comprising a pre-hydrogenation step, a hydrodeoxygenation (HDO) step and an isomerization step carried out countercurrently. Patent application EP1728844 describes a process for producing hydrocarbon compounds from a mixture of compounds of plant and animal origin. This process comprises a step of pretreating the mixture to remove contaminants, such as alkali metal salts, followed by a hydrodeoxygenation (HDO) step and an isomerization step.Patent application EP2084245 describes a process for producing a hydrocarbon mixture that can be used as diesel or in a diesel composition by hydrodeoxygenation of a mixture of biological origin containing fatty acid esters optionally in admixture with free fatty acids, for example vegetable oils such as sunflower oil, rapeseed oil, canola oil, palm oil or pine oil, followed by hydroisomerization on specific catalysts. Patent application EP2368967 describes such a process and the product obtained by this process. Application WO2016 / 185046 describes a process for obtaining a hydrocarbon fluid used according to the invention, in which the hydrocarbon fluid is obtained by a catalytic hydrogenation process at a temperature of 80 to 180°C and at a pressure of 50 to 160 bars of a deoxygenated and isomerized feedstock of biological origin.This process is advantageously used in the context of obtaining the hydrocarbon fluid in accordance with the present invention.

[0104] Advantageously, the raw material of biological origin contains less than 15 ppm of sulfur, preferably less than 8 ppm, preferably less than 5 ppm and more preferably less than 1 ppm according to standard EN ISO 20846. Ideally the feed does not include sulfur as a raw material of biosourced origin.

[0105] Before the hydrotreatment step, a prefractionation step can take place. A narrower cut at the inlet of the hydrogenation unit allows for a narrower cut at the outlet. Indeed, the boiling points of prefractionated cuts are between 220 and 330 °C while cuts that have not been prefractionated typically have boiling points between 150 and 360 °C.

[0106] The deoxygenated and isomerized feedstock from the HDO / ISO process is then hydrogenated.

[0107] The hydrogen used in the hydrogenation unit is typically highly purified hydrogen. "Highly purified" means hydrogen with a purity of, for example, greater than 99%, although other grades can also be used.

[0108] The hydrogenation step is carried out using catalysts. Typical hydrogenation catalysts can be either bulk or supported and may include the following metals: nickel, platinum, palladium, rhenium, rhodium, nickel tungstate, nickel-molybdenum, molybdenum, cobalt-molybdenum. Supports can be silica, alumina, silica-alumina, or zeolites.

[0109] A preferred catalyst is an alumina-supported nickel-based catalyst with a specific surface area ranging from 100 to 200 m2 / g of catalyst or a nickel-based bulk catalyst. Hydrogenation conditions are typically as follows: Pressure: 50 to 160 bars, preferably 80 to 150 bars and more preferably 90 to 120 bars; Temperature: 80 to 180 °C, preferably 120 to 160 °C and more preferably 150 to 160 °C; Hourly volumetric velocity (HVV): 0.2 to 5 hr-1, preferably 0.4 to 3 hr-1 and more preferably 0.5 to 0.8 hr-1; Hydrogen treatment rate: suitable for the conditions mentioned above and up to 200 Nm3 / tonnes of charge to be treated.

[0110] The temperature in the reactors is typically between 150 and 160°C with a pressure of approximately 100 bars while the hourly volumetric velocity is approximately 0.6 hr-1 with a treatment rate adapted according to the quality of the feedstock to be treated and the parameters of the first hydrogenation reactor.

[0111] Hydrogenation can take place in one or more reactors in series. Reactors may include one or more catalyst beds. Catalyst beds are usually fixed catalyst beds.

[0112] The hydrogenation process preferably comprises two or three reactors, preferably three reactors and is more preferably carried out in three reactors in series.

[0113] The first reactor allows the trapping of sulfur compounds and the hydrogenation of essentially all unsaturated compounds and up to about 90% of the aromatic compounds. The product from the first reactor contains substantially no sulfur compounds. In the second stage, i.e. in the second reactor, the hydrogenation of the aromatics continues and up to 99% of the aromatics are thereby hydrogenated.

[0114] The third stage in the third reactor is a finishing stage making it possible to obtain aromatic contents of less than or equal to 500 ppm, preferably less than or equal to 300 ppm, preferably less than or equal to 100 ppm, more preferably less than or equal to 50 ppm, and ideally less than or equal to 20 ppm even in the case of products with a high boiling point, for example greater than 300°C.

[0115] It is possible to use a reactor which has two or three or more catalytic beds. The catalysts may be present in varying or essentially equal amounts in each reactor; for three reactors, the amounts by weight may for example be 0.05-0.5 / 0.10-0.70 / 0.25-0.85, preferably 0.07-0.25 / 0.15-0.35 / 0.4-0.78 and more preferably 0.10-0.20 / 0.20-0.32 / 0.48-0.70.

[0116] It is also possible to use one or two hydrogenation reactors instead of three.

[0117] It is also possible for the first reactor to be composed of twin reactors operated alternately. This mode of operation allows in particular for easier loading and unloading of the catalysts: when the first reactor includes the saturated catalyst first (substantially all the sulfur is trapped on and / or in the catalyst) it must be changed often.

[0118] A single reactor can also be used in which two, three or more catalytic beds are installed.

[0119] It may be necessary to insert quench boxes (in the English sense of "reaction smothering") in the recycle system or between reactors to cool the effluents from one reactor to another or from one catalyst bed to another in order to control the temperatures and hydrothermal balance of each reaction. In a preferred embodiment, there are no cooling or smothering intermediaries.

[0120] According to one embodiment, the product from the process and / or the separated gases are at least partly recycled into the feed system of the hydrogenation reactors. This dilution helps to maintain the exothermicity of the reaction within controlled limits, particularly in the first stage. Recycling also allows heat exchange before the reaction and also better temperature control.

[0121] The effluent from the hydrogenation unit mainly contains the hydrogenated product and hydrogen. Flash separators are used to separate the effluents into the gas phase, mainly the residual hydrogen, and the liquid phase, mainly the hydrogenated hydrocarbon cuts. The process can be carried out using three flash separators: one at high pressure, one at intermediate pressure, and one at low pressure very close to atmospheric pressure.

[0122] The hydrogen gas that is collected at the top of the flash separators can be recycled into the hydrogenation unit feed system or at different levels in the hydrogenation units between the reactors.

[0123] According to one embodiment, the final product is separated at atmospheric pressure. It then feeds directly into a vacuum fractionation unit. Preferably, the fractionation will be carried out at a pressure between 10 and 50 mbar and more preferably at around 30 mbar.

[0124] Fractionation can be carried out in such a way that it is possible to simultaneously remove various hydrocarbon fluids from the fractionation column and their boiling temperature can be predetermined.

[0125] By adapting the feedstock through its initial and final boiling points, the hydrogenation reactors, separators and fractionation unit can be directly connected without the need for intermediate tanks. This integration of hydrogenation and fractionation allows for optimized thermal integration associated with a reduction in the number of devices and energy savings.

[0126] The hydrocarbon fluid according to the invention is ideally derived from the processing of raw materials of biological origin. The carbon in a biomaterial comes from plant photosynthesis and therefore from atmospheric CO 2 . The degradation (by degradation, we also understand combustion / incineration at the end of life) of these CO 2 materials therefore does not contribute to global warming because there is no increase in the carbon emitted into the atmosphere. The CO 2 assessment of biomaterials is therefore significantly better and contributes to reducing the carbon footprint of the products obtained (only the energy for manufacturing must be taken into account). On the contrary, a fossil material of origin also degraded into CO 2 will contribute to the increase in the CO 2 level and therefore to global warming. The hydrocarbon fluid used according to the invention will therefore have a carbon footprint that will be better than that of compounds obtained from a fossil source.

[0127] The term "bio-carbon" indicates that the carbon is of natural origin and comes from a biomaterial, as shown below. Bio-carbon content and biomaterial content are expressions indicating the same value. A material of renewable origin or biomaterial is an organic material in which the carbon comes from CO 2 recently fixed (on a human timescale) by photosynthesis from the atmosphere. A biomaterial (100% naturally occurring carbon) has a 14< C / 12< C isotopic ratio greater than 10-12, typically about 1.2 x 10-12, while a fossil material has a ratio of zero. This is because the isotopic 14< C is formed in the atmosphere and is then integrated by photosynthesis, on a timescale of a few decades at most. The half-life of 14< C is 5730 years. Thus, materials resulting from photosynthesis, namely plants in general, necessarily have a maximum content of the isotope 14< C.

[0128] The determination of biomaterial or bio-carbon content is given in accordance with ASTM D 6866-12, Method B (ASTM D 6866-06) and ASTM D 7026 (ASTM D 7026-04). ASTM D 6866 concerns the "Determination of Bio-Based Content of Natural Range Materials Using Radiocarbon and Isotope Ratio Mass Spectrometry Analysis", while ASTM D 7026 concerns "Sampling and Reporting of Results for Determination of Bio-Based Content by Carbon Isotope Analysis". The second standard mentions the first in its first paragraph.

[0129] The first standard describes a test for measuring the 14<C / 12<C ratio of a sample and comparing it with the 14<C / 12<C ratio of a reference sample of 100% renewable origin, to give a relative percentage of renewable C in the sample. The standard is based on the same concepts as 14<C dating, but without applying the dating equations. The ratio thus calculated is reported as "pMC" (percentage Modern Carbon). If the material to be analyzed is a mixture of biomaterial and fossil material (without radioactive isotope), the pMC value obtained is directly correlated to the amount of biomaterial present in the sample. The reference value used for 14C dating is a value dating from the 1950s. This year was selected due to the existence of nuclear tests in the atmosphere that introduced large quantities of isotopes into the atmosphere after this date.The 1950 reference corresponds to a pMC value of 100. Taking into account thermonuclear tests, the current value to be retained is approximately 107.5 (which corresponds to a correction factor of 0.93). The radioactive carbon signature of a modern plant is therefore 107.5. A signature of 54 pMC and 99 pMC therefore corresponds to a quantity of biomaterial in the sample of 50% and 93% respectively.

[0130] The hydrocarbon fluid in accordance with the invention has a biomaterial content of at least 90%. This content is advantageously higher, in particular greater than or equal to 95%, preferably greater than or equal to 98% and advantageously equal to 100%.

[0131] According to one embodiment, the isotopic ratio 14< C / 12< C of the hydrocarbon fluid used in the invention is between 1.15 and 1.2 x 10 12< .

[0132] In addition to a particularly high biomaterial content, the hydrocarbon fluid according to the invention has particularly good biodegradability. The biodegradation of an organic chemical refers to the reduction of the complexity of chemical compounds through the metabolic activity of microorganisms. Under aerobic conditions, microorganisms convert organic substances into carbon dioxide, water and biomass. The OECD 306 method is used for the assessment of the biodegradability of individual substances in seawater. According to this method, the hydrocarbon fluid has a biodegradability at 28 days of at least 60%, preferably at least 70%, more preferably at least 75% and advantageously at least 80%.

[0133] The OECD 306 method is as follows: The closed bottle method consists of dissolving a predetermined amount of the test substance in a control medium at a concentration typically of 2-10 mg / L, with one or more concentrations optionally being used. The solution is kept in a filled closed bottle protected from light at a constant temperature in the range 15-20°C. The degradation is monitored by oxygen analysis over a period of 28 days. 24 bottles are used (8 for the test substance, 8 for the reference compound and 8 for nutrients). All analyses are carried out on several bottles. At least 4 dissolved oxygen determinations are carried out (day 0, 5, 15 and 20) using a chemical or electrochemical method.

[0134] According to a particular embodiment of the invention, the hydrocarbon fluid comprises: a weight content of isoparaffins ranging from 95 to 100% and preferably from 98% to 100% relative to the total weight of the hydrocarbon fluid, and a weight content of normal paraffins less than or equal to 5% and preferably less than or equal to 2% relative to the total weight of the hydrocarbon fluid; and a weight content of naphthenic compounds less than or equal to 0.5% and preferably less than or equal to 100 ppm relative to the total weight of the hydrocarbon fluid; and a weight content of aromatic compounds less than or equal to 300 ppm, preferably less than or equal to 100 ppm, more preferably less than or equal to 50 ppm and advantageously less than or equal to 20 ppm, relative to the total weight of the hydrocarbon fluid.

[0135] According to a particular embodiment of the invention, the hydrocarbon fluid has a weight content of isoparaffins ranging from 98% to 100% relative to the total weight of the hydrocarbon fluid, and a kinematic viscosity at 40°C less than or equal to 5 cSt, preferably less than or equal to 4 cSt and preferentially less than or equal to 3.5 cSt.

[0136] Advantageously, a composition used according to the invention comprises from 80% to 99.5%, even more preferably from 80% to 98%, advantageously from 90% to 97% by weight of at least one base oil or at least one hydrocarbon fluid having a boiling point greater than or equal to 50°C. Flame retardant

[0137] In the context of the present invention, at least one flame retardant is incorporated, at least partially in an encapsulated form, in the cooling composition of a propulsion system of an electric or hybrid vehicle, corresponding to the formula (I) RF -LR H (I) in which RF is a perfluorinated or partially fluorinated group, RH is a hydrocarbon group, and L is a linker.

[0138] As used herein, the term "partially fluorinated group" means that at least 60% of the hydrogen atoms in the group concerned have been replaced by fluorine atoms, for example between 60 and 80%.

[0139] In the context of the present invention, the expression "at least partially in an encapsulated form" is intended to mean that at least a portion of the flame retardant of formula (I) is in an encapsulated form in the cooling composition, in particular at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, relative to the total weight of flame retardant of formula (I) present in the composition.

[0140] In the context of the present invention, the term "encapsulated" means that the flame retardant of formula (I) is formulated within individualized particles. More precisely, these particles have a core-shell structure, the core consisting of at least one flame retardant of formula (I) and the shell enclosing the core and separating it from the other components of the cooling composition and thus playing a role in protecting the core of the capsule from the external environment.

[0141] Without the applicant being bound by any theory, it is described that the encapsulation of the flame retardant makes it possible to control its release under conditions of runaway battery operation, in particular when the temperature reaches a given temperature, in particular a temperature corresponding to heating detrimental to the safety of the propulsion system of the electric or hybrid vehicle, likely to be caused by an incident, for example of the explosion type, at the battery. The wall of the capsule can thus, for example, disintegrate when a critical temperature is reached, thus allowing the dilution of the flame retardant in the base oil, and therefore confer on the composition properties of reducing the flammability of said composition.

[0142] Once the flame retardant is released into the cooling composition, it can then fully perform its fire-fighting role through its presence in the composition in contact with the battery.

[0143] According to a particular embodiment, the RF group comprises between 1 and 22, preferably between 1 and 20, more particularly between 1 and 16 carbon atoms. Said group may optionally be interrupted by 1 to 4 heteroatoms chosen from a nitrogen atom and an oxygen atom. This group may also be linear or branched.

[0144] Advantageously, it is a perfluorinated or partially fluorinated (C 1 -C 16 )alkyl group optionally interrupted by one or two heteroatoms chosen from a nitrogen atom and an oxygen atom.

[0145] Such an RF group can for example be chosen from the following groups: CF 3 (CF 2 ) m -, C(CF 3 ) 3 (CF 2 ) m -, (CF 3 ) 2 CF(CF 2 ) m -, (CF 3 ) 2 CF-, and (CF 3 )CF 2 -, (CF 3 )(CF 2 ) 3 -, with m being an integer between 1 and 15, m being an integer between 0 and 14.

[0146] These examples are not exhaustive.

[0147] According to another particular embodiment, the RH group comprises between 1 and 22 carbon atoms, preferably between 1 and 20, even more preferably between 1 and 16 carbon atoms. According to a particular embodiment, this RH group may comprise between 1 and 4 heteroatoms chosen from a nitrogen atom and an oxygen atom. This group may also be linear or branched. It may also be saturated or comprise from 1 to 4 unsaturations.

[0148] According to another embodiment, the RH group may preferably comprise between 3 and 22 carbon atoms, more preferably between 3 and 18, for example between 5 and 15, or even between 10 and 15 carbon atoms.

[0149] Advantageously, it is a (C 1 -C 15 )alkyl group, in particular (C 3 -C 15 )alkyl), or (C 2 -C 15 )alkenyl, said group being optionally substituted by a hydrocarbon cycle such as the (C 3 -C 6 )cycloalkyl, phenyl or benzyl group.

[0150] Such an HR group may in particular be chosen from the following groups, without however being limited to: -(CH 2 ) n CH 3 , -(CH 2 ) p C 6 H 4 , -(CH 2 ) q O(CH 2 ) r CH 3 , and -(CH 2 ) s C=C(CH 2 )tCH 3 with n being an integer which may be between 1 and 21, for example between 2 and 21, in particular between 7 and 21, p being between 1 and 16, in particular between 2 and 10, q and r being independently between 1 and 16, with q+r being less than or equal to 21 and advantageously greater than 7, s and t being independently between 1 and 16, with s+t being less than or equal to 19 and advantageously greater than 5.

[0151] The linker L can in particular be chosen from the following divalent groups: -CH 2 -, -CH=CH-, -O-, -S- or -PO 4 -.

[0152] According to a particular embodiment, the flame retardant may be chosen from the compounds of formula (I) in which RF is a perfluorinated or partially fluorinated (C 2 -C 12 )alkyl group, RH is a (C 1 -C 12 )alkyl group, in particular (C 3 -C 12 )alkyl, in particular (C 6 -C 12 )alkyl or (C 2 -C 12 )alkenyl, in particular (C 6 -C 12 )alkenyl, said group being optionally substituted by a hydrocarbon ring such as the (C 3 -C 6 )cycloalkyl, phenyl or benzyl group, and said group being able to be interrupted by 1 or 2 heteroatoms chosen from nitrogen or oxygen, and L is a linker chosen from -CH 2 -, -CH=CH- and -O-.

[0153] It is understood within the scope of the present invention that the flame retardant of formula (I) as defined above may be in the form of a mixture of flame retardants of formula (I) as defined above.

[0154] For the purposes of the present invention, the following terms are defined as follows: "(C 1 -C x ) alkyl" refers to a saturated hydrocarbon chain having from 1 to x carbon atoms, linear or branched, for example a (C 1 -C 12 )alkyl group. Non-limiting examples include methyl, ethyl, 1-propyl, 2-propyl, butyl, pentyl, hexyl, heptyl, and decyl, "(C 2 -C x ) alkenyl" refers to a hydrocarbon chain having unsaturations and having from 2 to x carbon atoms, linear or branched, for example a (C 2 -C 12 )alkyl group. Non-limiting examples include the following groups: ethylene, propylene, butylene, pentylene, hexylene and decylene "(C 3 -C 6 )cycloalkyl", with a saturated and cyclic hydrocarbon chain. Non-limiting examples include the following groups: cyclopropyl, cyclobutyl, cyclopentyl and cyclohexyl.

[0155] According to one embodiment, the flame retardant of formula (I) is completely in an encapsulated form in a cooling composition according to the invention.

[0156] In the context of the present invention, the expression "totally in an encapsulated form" is intended to mean more precisely that the composition comprises less than 5% by weight, preferably less than 2% by weight, more preferably less than 0.5% by weight of flame retardant of formula (I) not in an encapsulated form, relative to the total weight of flame retardant of formula (I) present in the composition.

[0157] Advantageously, 100% by weight of the flame retardant of formula (I) is in an encapsulated form, relative to the total weight of flame retardant of formula (I) present in the composition.

[0158] According to the present invention, the flame retardant(s) of formula (I) is / are present in a content of between 0.5% and 40% by weight, relative to the total weight of the composition in accordance with the present invention, in particular in a content of between 2% and 30% by weight, even more particularly in a content of between 2% and 20% by weight, advantageously between 3% and 10% by weight.

[0159] In terms of formulation of the composition according to the present invention, all methods known to those skilled in the art can be used for the encapsulation of at least one flame retardant and for the additivation of the oil with at least one flame retardant in an encapsulated form. Capsules

[0160] The incorporation of at least a portion of the flame retardant(s) into the base oil may be carried out via an encapsulation process as defined more precisely below and in particular described in document EP 3 144 059.

[0161] Such an encapsulation process allows the production of capsules of controlled size, in particular with an average size of less than 5 µm, while allowing the size of the capsules to be precisely controlled and adjusted.

[0162] According to this embodiment, the flame retardant capsules are directly formulated into the base oil or hydrocarbon fluid.

[0163] The microcapsules according to the invention may have an average diameter less than or equal to 10 µm, preferably ranging from 0.1 µm to 5 µm, more preferably ranging from 0.1 µm to 3 µm.

[0164] The formulation of the flame retardant of formula (I) in the form of capsules advantageously makes it possible to control its release into the cooling composition.

[0165] Any method of releasing the flame retardant of formula (I) known to those skilled in the art may be implemented, provided that this release, partial or total, is carried out as soon as the battery undergoes heating which is detrimental to the safety of the propulsion system of the electric or hybrid vehicle.

[0166] Generally, the release of the flame retardant is achieved by rupture of the capsule, caused either by a predetermined condition, such as a variation in pH, temperature or pressure, or by a chemical reaction with a compound brought into contact with the capsule.

[0167] In particular, capsule rupture can be caused by an increase in temperature, by acid degradation of the capsule shell or by hydrolysis of this shell in the presence of water.

[0168] According to one embodiment, the flame retardant is released into the cooling composition by melting or degradation of the casing following an increase in temperature. In particular, the casing of the capsules may be formed from a material capable of melting or degrading at a temperature corresponding to a critical temperature beyond which a runaway effect of the battery can be expected.

[0169] Generally speaking, as soon as the battery in operation exceeds temperatures of the order of 50 to 60°C, there is a high risk of ignition, or even explosion, of the battery. Thus, the critical temperature beyond which the material constituting the battery is likely to melt or degrade may be greater than or equal to 40°C, in particular between 40°C and 60°C.

[0170] Examples of materials that may constitute the shell of the capsules defined above are polyethers, polyesters, polyurethanes, polyureas, polyethylene glycols, polypropylene glycols, polyamides, polyacetals, polyimides, polyolefins, polysulfides, and polydimethylsiloxanes. Additives Radical inhibitor

[0171] The cooling composition according to the invention may further comprise at least one radical inhibitor.

[0172] Such radical inhibitors are per se known to those skilled in the art and may have different chemical natures and in particular belong to different chemical families.

[0173] In terms of formulation of the composition according to the present invention, all methods known to those skilled in the art can be used for this additivation of the oil.

[0174] Among the radical inhibitors, we can notably cite phosphorus radical inhibitors.

[0175] Among the phosphorus radical inhibitors, a distinction is made between compounds for which the phosphorus is a P(V) or pentavalent phosphorus and compounds for which the phosphorus is a P(III) or trivalent phosphorus.

[0176] Among these compounds in the form of pentavalent phosphorus, P(V), we can notably cite the phosphate family and in particular, triethylphosphate, trimethylphosphate, possibly fluorinated alkylphosphates or even arylphosphates.

[0177] As fluorinated alkylphosphate, we can notably cite tris (2,2,2-trifluoroethyl)phosphate.

[0178] Examples of arylphosphates include triphenylphosphate, tricresylphosphate and trixylenylphosphate.

[0179] Still among these compounds in the P(V) form, we can notably cite the phosphazene family. In this family, which is characterized by the fact that its representatives have at least one double bond between a pentavalent phosphorus atom and a nitrogen atom, cyclic compounds are favored. We can notably cite hexamethoxycyclotriphosphazene.

[0180] Among these compounds in the form of trivalent phosphorus, P(III), we can notably cite the phosphite family. In this family, we can notably cite tris(2,2,2-trifluoroethyl)phosphite.

[0181] The cooling composition in accordance with the invention may further comprise at least one additional flame retardant, different from the flame retardant of formula (I) defined above.

[0182] Among these other flame retardants, we can notably cite halogenated compounds other than fluorinated ones.

[0183] It is up to the person skilled in the art to adjust the proportions of the various constituents of the composition, in particular the fluid base, the flame retardant of formula (I) as defined above and possibly the radical inhibitor and / or additional flame retardants to comply with the viscosity required according to the invention, and possibly the density of the composition.

[0184] According to a particular embodiment, a cooling composition according to the invention comprises at least one hydrocarbon fluid comprising a content greater than or equal to 90% by weight, in particular greater than or equal to 95% by weight, and even more advantageously greater than or equal to 98% by weight of isoparaffins, relative to the total weight of hydrocarbon fluid, at least one flame retardant of formula (I) as defined above being at least partially in an encapsulated form, and optionally at least one phosphorus radical inhibitor.

[0185] According to a particular embodiment, a cooling composition according to the invention comprises at least one hydrocarbon fluid having a weight content of isoparaffins ranging from 98% to 100% relative to the total weight of the hydrocarbon fluid, and a kinematic viscosity at 40°C less than or equal to 5 cSt, preferably less than or equal to 4 cSt and preferentially less than or equal to 3.5 cSt, at least one flame retardant of formula (I) as defined above being at least partially in an encapsulated form, and optionally a phosphorus radical inhibitor, in particular as more particularly described above.

[0186] Alternatively, a composition according to the invention may further comprise one or more additives as defined more precisely in the remainder of the text. Other additives

[0187] According to a variant of the invention, the cooling composition according to the present invention further comprises additives modulating the properties of the base oil.

[0188] The additives that can be incorporated into a composition according to the invention can be chosen from friction modifiers, detergents, anti-wear additives, extreme pressure additives, dispersants, antioxidants, pour point improvers, anti-foams and mixtures thereof.

[0189] It is understood that the nature and quantity of additives used are chosen so as not to affect the combined properties of cooling power of the composition according to the invention and fire protection.

[0190] These additives can be introduced in isolation and / or in the form of a mixture similar to those already available for sale for formulations of commercial lubricants for vehicle engines, with performance levels as defined by the ACEA (Association of European Automobile Manufacturers) and / or the API (American Petroleum Institute), well known to those skilled in the art.

[0191] Anti-wear additives and extreme pressure additives protect friction surfaces by forming a protective film adsorbed on these surfaces.

[0192] There is a wide variety of anti-wear additives. Preferably for the composition according to the invention, the anti-wear additives are chosen from phosphosulfur additives such as metal alkylthiophosphates, in particular zinc alkylthiophosphates, and more specifically zinc dialkyldithiophosphates or ZnDTP. The preferred compounds are of formula Zn((SP(S)(OR 2< )(OR 3< )) 2 , in which R 2< and R 3< , identical or different, independently represent an alkyl group, preferably an alkyl group comprising from 1 to 18 carbon atoms.

[0193] Amine phosphates are also anti-wear additives that can be used in a composition according to the invention. However, the phosphorus provided by these additives can act as a poison for automobile catalytic systems because these additives generate ash. These effects can be minimized by partially substituting the amine phosphates with additives that do not provide phosphorus, such as, for example, polysulfides, in particular sulfur-containing olefins.

[0194] A cooling composition according to the invention may comprise from 0.01 to 6% by weight, preferably from 0.05 to 4% by weight, more preferably from 0.1 to 2% of anti-wear additives and extreme pressure additives, by mass relative to the total weight of the composition.

[0195] According to a particular embodiment, a cooling composition according to the invention is free of anti-wear additives and extreme pressure additives. In particular, a cooling composition according to the invention is advantageously free of phosphate additives.

[0196] A cooling composition according to the invention may comprise at least one friction-modifying additive. The friction-modifying additive may be chosen from a compound providing metallic elements and an ash-free compound. Among the compounds providing metallic elements, mention may be made of transition metal complexes such as Mo, Sb, Sn, Fe, Cu, Zn, the ligands of which may be hydrocarbon compounds comprising oxygen, nitrogen, sulfur or phosphorus atoms. The ash-free friction-modifying additives are generally of organic origin and may be chosen from monoesters of fatty acids and polyols, alkoxylated amines, alkoxylated fatty amines, fatty epoxides, borate fatty epoxides; fatty amines or fatty acid glycerol esters. According to the invention, the fatty compounds comprise at least one hydrocarbon group comprising from 10 to 24 carbon atoms.

[0197] A cooling composition according to the invention may comprise from 0.01 to 2% by weight or from 0.01 to 5% by weight, preferably from 0.1 to 1.5% by weight or from 0.1 to 2% by weight of friction modifying additive, relative to the total weight of the composition.

[0198] Advantageously, a cooling composition according to the invention is free of friction modifying additive.

[0199] A cooling composition according to the invention may comprise at least one antioxidant additive.

[0200] The antioxidant additive generally helps to delay the degradation of the composition in service. This degradation can notably result in the formation of deposits, the presence of sludge or an increase in the viscosity of the composition.

[0201] Antioxidant additives act in particular as radical inhibitors or hydroperoxide destroyers. Among the commonly used antioxidant additives, mention may be made of phenolic type antioxidant additives, amine type antioxidant additives, phosphosulfur antioxidant additives. Some of these antioxidant additives, for example phosphosulfur antioxidant additives, may be ash-generating. Phenolic antioxidant additives may be ash-free or in the form of neutral or basic metal salts. The antioxidant additives may in particular be chosen from sterically hindered phenols, sterically hindered phenol esters and sterically hindered phenols comprising a thioether bridge, diphenylamines, diphenylamines substituted by at least one C 1 -C 12 alkyl group, N,N'-dialkyl-aryl-diamines and mixtures thereof.

[0202] Preferably according to the invention, the sterically hindered phenols are chosen from compounds comprising a phenol group of which at least one vicinal carbon of the carbon carrying the alcohol function is substituted by at least one C 1 - C 10 alkyl group, preferably a C 1 - C 6 alkyl group, preferably a C 4 alkyl group, preferably by the tert-butyl group.

[0203] Amino compounds are another class of antioxidant additives that can be used, optionally in combination with phenolic antioxidant additives. Examples of amine compounds are aromatic amines, for example aromatic amines of the formula NR 4< R 5< R 6< in which R 4< represents an aliphatic group or an aromatic group, optionally substituted, R 5< represents an aromatic group, optionally substituted, R 6< represents a hydrogen atom, an alkyl group, an aryl group or a group of the formula R 7< S(O) z R 8< in which R 7< represents an alkylene group or an alkenylene group, R 8< represents an alkyl group, an alkenyl group or an aryl group and z represents 0, 1 or 2.

[0204] Sulfurized alkyl phenols or their alkali and alkaline earth metal salts can also be used as antioxidant additives.

[0205] Another class of antioxidant additives is copper compounds, e.g. copper thio- or dithio-phosphates, copper salts of carboxylic acids, dithiocarbamates, sulphonates, phenates, copper acetylacetonates. Copper I and II salts, succinic acid or anhydride salts can also be used.

[0206] A cooling composition according to the invention may contain all types of antioxidant additives known to those skilled in the art.

[0207] Advantageously, a cooling composition according to the invention comprises at least one ash-free antioxidant additive.

[0208] A cooling composition according to the invention may comprise from 0.5 to 2% by weight of at least one antioxidant additive, relative to the total weight of the composition.

[0209] A cooling composition according to the invention may also comprise at least one detergent additive.

[0210] Detergent additives generally reduce the formation of deposits on the surface of metal parts by dissolving secondary oxidation and combustion products.

[0211] The detergent additives usable in a cooling composition according to the invention are generally known to those skilled in the art. The detergent additives may be anionic compounds comprising a long lipophilic hydrocarbon chain and a hydrophilic head. The associated cation may be a metal cation of an alkali or alkaline earth metal.

[0212] The detergent additives are preferably chosen from alkali metal or alkaline earth metal salts of carboxylic acids, sulfonates, salicylates, naphthenates, as well as phenate salts. The alkali and alkaline earth metals are preferably calcium, magnesium, sodium or barium.

[0213] These metal salts generally comprise the metal in a stoichiometric quantity or in excess, i.e. in a quantity greater than the stoichiometric quantity. These are then overbased detergent additives; the excess metal providing the overbased character to the detergent additive is then generally in the form of an oil-insoluble metal salt, for example a carbonate, a hydroxide, an oxalate, an acetate, a glutamate, preferably a carbonate.

[0214] A cooling composition according to the invention may, for example, comprise from 2 to 4% by weight of detergent additive, relative to the total weight of the composition.

[0215] A cooling composition according to the invention may also comprise at least one pour point depressant additive.

[0216] By slowing the formation of paraffin crystals, pour point depressant additives generally improve the cold behavior of the composition.

[0217] Examples of pour point depressant additives include polyalkyl methacrylates, polyacrylates, polyarylamides, polyalkylphenols, polyalkylnaphthalenes, alkylated polystyrenes.

[0218] Also, a cooling composition according to the invention may comprise at least one dispersing agent.

[0219] The dispersing agent may be chosen from Mannich bases, succinimides and their derivatives.

[0220] A cooling composition according to the invention may, for example, comprise from 0.2 to 10% by weight of dispersing agent, relative to the total weight of the composition.

[0221] As mentioned above, water is not compatible with direct contact with an electric or hybrid vehicle propulsion system, such as the motor, power electronics and battery.

[0222] Thus, a composition according to the invention is free of water. By " water-free " for the purposes of the present invention, it is understood that the composition comprises less than 1% by weight of water, preferably less than 0.1% by weight, does not comprise water.

[0223] According to a particular embodiment, a composition according to the invention comprises, or even consists of: from 80% to 99.5% by weight, preferably between 80% and 98% by weight, more preferably from 90% to 97% by weight, of at least one base oil, or of at least one hydrocarbon fluid having a boiling point greater than or equal to 50°C, preferably chosen from hydrocarbons comprising at least 8 carbon atoms, for example between 8 and 22 carbon atoms; from 0.5% to 40% by weight, preferably from 2% to 30% by weight, more preferably from 2% to 20% by weight, of one or more flame retardants corresponding to formula (I), in particular in which RF is a perfluorinated or partially fluorinated (C 2 -C 12 )alkyl group, RH is a (C 6 -C 12 )alkyl, (C 6 -C 12 )alkenyl group, said group being optionally substituted by a (C 3 -C 6 )cycloalkyl, phenyl or benzyl group, and said group possibly being interrupted by 1 or 2 heteroatoms chosen from nitrogen or oxygen, and L is a linker chosen from -CH 2 -, -CH=CH- and -O-;and optionally from 0.1% to 10% by weight of one or more additives chosen from phosphorus radical inhibitors, friction modifiers, detergents, anti-wear additives, extreme pressure additives, dispersants, antioxidants, pour point improvers, anti-foams and mixtures thereof; the contents being expressed in relation to the total weight of the composition. APPLICATION

[0224] As indicated previously, a composition according to the invention can be used, due to its combined properties in terms of cooling and fire retardant, both as a cooling fluid for a propulsion system of an electric or hybrid vehicle, and more particularly of the power electronics and batteries, and as a fluid delaying and / or preventing the spread of fire for the batteries.

[0225] Advantageously, the composition according to the invention is brought into contact with the battery, by immersion or semi-immersion to play its dual role of cooling and fire protection with respect to the batteries.

[0226] By "immersion" is meant that the entire battery is surrounded by the cooling composition according to the present invention. By "semi-immersion" is meant that only a portion of the battery is in contact with said composition.

[0227] Alternatively, the cooling composition according to the invention is advantageously brought into direct contact with the batteries by methods described below.

[0228] Suitable batteries for the propulsion systems of electric or hybrid vehicles include Li-ion batteries and Nickel-Cadmium batteries.

[0229] An electric motor is typically powered by an electric battery (2). Lithium-ion batteries are the most common type of battery used in electric vehicles. The development of increasingly powerful and smaller batteries means that the problem of cooling this battery arises. Indeed, as soon as the battery exceeds temperatures of around 50 to 60°C, there is a high risk of ignition, or even explosion, of the battery. There is also a need to keep the battery at a temperature above approximately 20 to 25°C to prevent the battery from discharging too quickly and to extend its lifespan.

[0230] A composition of the invention can thus be used to cool the battery of an electric or hybrid vehicle and to delay and / or prevent the spread of fire.

[0231] The composition according to the invention can be injected under fairly high pressure into the zones to be cooled in the propulsion system of an electric or hybrid vehicle, the resulting shear at the injector advantageously making it possible to reduce the viscosity of the fluid at the injection zone, compared to the kinematic viscosity at rest, and thus, to further increase the cooling potential of the composition.

[0232] As shown schematically in Figure 1 , the propulsion system of an electric or hybrid vehicle, notably comprises the electric motor part (1). This typically comprises power electronics (11) connected to a stator (13) and a rotor (14).

[0233] The stator consists of coils, particularly copper coils, which are alternately energized by an electric current. This generates a rotating magnetic field. The rotor itself consists of coils, permanent magnets, or other magnetic materials and is rotated by the rotating magnetic field.

[0234] The power electronics (11), stator (13) and rotor (14) of a propulsion system (1) are parts whose structure is complex and generates a large amount of heat during operation of the motor. It is therefore imperative to ensure cooling of the electric motor and the power electronics.

[0235] A bearing (12) is generally integrated between the stator (13) and the rotor (14)

[0236] A propulsion system of an electric or hybrid vehicle also includes a transmission, and in particular a speed reducer (3) which makes it possible to reduce the rotation speed at the output of the electric motor and to adapt the speed transmitted to the wheels, at the same time making it possible to control the speed of the vehicle.

[0237] Thus, the invention relates to the use of a composition as described above for cooling the battery and the power electronics and for securing a propulsion system of an electric or hybrid vehicle, and in particular the battery, against fire.

[0238] Thus, the invention has the advantage of allowing the use of a single composition combining cooling and flame-retardant or flame-retardant properties, as a cooling and fire-protection fluid for a battery in an electric or hybrid vehicle, while ensuring a cooling function for the power electronics of an electric or hybrid vehicle.

[0239] According to a particular embodiment, the composition of the invention plays, in addition to its cooling and flame retardant role, a lubricating role. This triple role can in particular be achieved when the flame retardant of formula (I) as defined above is used, at least partially in an encapsulated form, in a base oil, as previously described.

[0240] Indeed, hydrocarbon fluids with a boiling point greater than or equal to 50°C as described above do not allow the lubrication role to be ensured.

[0241] In other words, according to this embodiment, the composition comprises at least one base oil and at least one flame retardant corresponding to the formula (I) RF -LR H (I) in which RF is a perfluorinated or partially fluorinated group, in particular comprising from 1 to 22, preferably from 1 to 20, even more preferably from 1 to 16 carbon atoms, RH is a hydrocarbon group, in particular comprising from 1 to 22, preferably from 1 to 20, even more preferably from 1 to 16 carbon atoms, and L is a linker, said flame retardant of formula (I) being at least partially in an encapsulated form.

[0242] Still according to this particular embodiment, a composition can be used, due to its joint properties in terms of lubrication, cooling and fire retardant, both as a lubricating fluid for the engine and transmission, as a cooling fluid for a propulsion system of an electric or hybrid vehicle, and more particularly for the engine, power electronics and batteries, and as a fluid delaying and / or preventing the spread of fire for the batteries.

[0243] The invention thus also relates to the use of a composition as defined above for lubricating, cooling and securing a propulsion system of an electric or hybrid vehicle.

[0244] Still according to this embodiment, the composition makes it possible in particular to ensure within an electric or hybrid vehicle, in addition to the cooling function and the fire protection function of the battery, the lubrication function and protection of the components in contact against wear as well as the cooling of the engine and the power electronics.

[0245] A propulsion system of an electric or hybrid vehicle also includes a transmission, and in particular a speed reducer (3) which makes it possible to reduce the rotation speed at the output of the electric motor and to adapt the speed transmitted to the wheels, at the same time making it possible to control the speed of the vehicle.

[0246] This reducer is subject to high frictional stresses and therefore needs to be lubricated appropriately to prevent it from being damaged too quickly.

[0247] Thus, a composition according to this particular embodiment makes it possible to lubricate the transmission, in particular the reducer, in an electric or hybrid vehicle.

[0248] Thus, the invention relates to the use of a composition as described above, for cooling the battery, the engine, and the power electronics, for lubricating the engine and the transmission and for securing against fire a propulsion system of an electric or hybrid vehicle, and in particular the battery.

[0249] In particular, such a composition makes it possible to cool the power electronics and / or the rotor and / or the stator of the electric motor. It can also provide lubrication for the bearings located between the rotor and the stator of an electric motor of an electric or hybrid vehicle.

[0250] Thus, this embodiment of the invention has the advantage of allowing the use of a single composition combining cooling and flame-retardant or flame-retardant properties, as a cooling and fire-protection fluid for a battery in an electric or hybrid vehicle, while ensuring a lubrication and cooling function for the propulsion system of an electric or hybrid vehicle as a whole.

[0251] The invention also relates to a method for cooling and fireproofing at least one battery of a propulsion system of an electric or hybrid vehicle, comprising at least one step of bringing at least one battery, in particular a Lithium-ion or Nickel-Cadmium battery, into contact with a composition as defined above.

[0252] According to a particular embodiment, the contacting step consists of immersion or semi-immersion of the battery in said composition or even injection of said composition onto the surface of the battery.

[0253] All of the characteristics and preferences described for the cooling composition according to the invention as well as for its uses also apply to this method.

[0254] Cooling by a composition according to the invention can be implemented by any method known to those skilled in the art.

[0255] The battery may be immersed or semi-immersed, static or circulating, in said composition.

[0256] Examples of direct contact include cooling by injection, jet, spraying or even by forming a mist from the composition according to the invention under pressure and by gravity on the battery.

[0257] Advantageously, the composition is injected by jet under fairly high pressure into the areas to be cooled of the propulsion system. Advantageously, the shear resulting from this injection makes it possible to reduce the viscosity of the fluid at the injection zone, compared to the kinematic viscosity at rest, and thus, to further increase the cooling potential of the composition.

Claims

1. Composition for cooling a propulsion system of an electric or hybrid vehicle, comprising: (i) at least one base oil, or at least one hydrocarbon fluid with a boiling point of greater than or equal to 50°C; and (ii) at least one fire retardant corresponding to formula (I)         RF-L-RH     (I) in which RF is a perfluorinated or partially fluorinated group, in particular comprising from 1 to 22, preferably from 1 to 20 and even more preferentially from 1 to 16 carbon atoms, RH is a hydrocarbon group, in particular comprising from 1 to 22, preferably from 1 to 20 and even more preferentially from 1 to 16 carbon atoms, and L is a linker, said fire retardant of formula (I) being at least partially, in particular totally, in an encapsulated form; said fire retardant of formula (I) being present in a content of between 0.5% and 40% by weight, relative to the total weight of the composition; said composition being free from water.

2. Composition according to the preceding claim, characterized in that RF is a perfluorinated or partially fluorinated (C1-C16) alkyl group, optionally interrupted by one or two heteroatoms chosen from a nitrogen atom and an oxygen atom, and RH is a (C1-C15) alkyl, especially (C3-C15) alkyl, or (C2-C15) alkenyl group, said group being optionally substituted by a hydrocarbon ring such as the (C3-C6)cycloalkyl, phenyl or benzyl group.

3. Composition according to either of Claims 1 and 2, characterized in that L is chosen from the following divalent groups: -CH2-, -CH=CH-, -O-, -S- or -PO4-.

4. Composition according to any one of the preceding claims, characterized in that the fire retardant of formula (I) is in a content of between 2% and 30% by weight, even more particularly in a content of between 2% and 20% by weight, advantageously between 3% and 10% by weight, relative to the total weight of the composition.

5. Composition according to any one of Claims 1 to 4, characterized in that the hydrocarbon fluid has a boiling point of between 50°C and 350°C, in particular between 60°C and 250°C and even more particularly between 80°C and 200°C.

6. Composition according to any one of Claims 1 to 4, characterized in that the hydrocarbon fluid is totally saturated, preferably in that the components of the hydrocarbon fluid are chosen from isoparaffins comprising from 12 to 30 carbon atoms, preferentially from 13 to 19 carbon atoms and more preferentially from 14 to 18 carbon atoms.

7. Composition according to any one of Claims 1 to 4, characterized in that it comprises at least one base oil, in particular a fluid base formed from one or more base oils, having a kinematic viscosity, measured at 100°C according to the standard ASTM D445, ranging from 1.5 to 8 mm2 / s, in particular from 1.5 to 6.1 mm2 / s, more particularly from 1.5 to 4.1 mm2 / s and even more particularly from 1.5 to 2.1 mm2 / s.

8. Composition according to any one of the preceding claims, characterized in that the base oil is chosen from synthetic oils, such as certain esters of carboxylic acids and of alcohols, from poly-α-olefins, and from polyalkylene glycols obtained by polymerization or copolymerization of alkylene oxides comprising from 2 to 8 carbon atoms, in particular from 2 to 4 carbon atoms.

9. Composition according to any one of the preceding claims, said composition also comprising at least one additive chosen from friction modifiers, detergents, anti-wear additives, extreme-pressure additives, dispersants, antioxidants, pour-point improvers, antifoams and mixtures thereof or at least one free-radical inhibitor and / or at least one additional fire retardant, other than the fire retardant of formula (I) as defined according to any one of Claims 1 to 3.

10. Composition according to the preceding claim, characterized in that the free-radical inhibitor is chosen from compounds taking the form of a pentavalent phosphorus of the phosphate or phosphazene family or in the form of a trivalent phosphorus of the phosphite family and the additional fire retardant is chosen from halogenated compounds other than fluorinated compounds.

11. Use of at least one fire retardant of formula (I) as defined according to any one of Claims 1 to 3, at least partially in an encapsulated form, in a composition for cooling a propulsion system of an electric or hybrid vehicle, including at least one battery, in order to confer upon it ignition-resistance properties.

12. Use according to the preceding claim, characterized in that the composition also comprises at least one free-radical inhibitor and / or at least one additional fire retardant, in particular as defined according to Claim 10.

13. Use according to either of Claims 11 and 12, characterized in that the fire retardant of formula (I) is present in the composition in a content of between 0.5% and 40% by weight, relative to the total weight of the composition, in particular in a content of between 2% and 30% by weight, even more particularly in a content of between 2% and 20% by weight, advantageously between 3% and 10% by weight.

14. Process for cooling and fire-protecting a battery of a propulsion system of an electric or hybrid vehicle, comprising at least one step of placing at least one battery, in particular a lithium-ion or nickel-cadmium battery, in contact with a composition as described according to any one of Claims 1 to 10.

15. Process according to Claim 14, characterized in that said at least one battery is in immersion or semi-immersion, static or in circulation, in said composition or said composition is placed in direct contact with the batteries by injection, by jet, by spraying or by formation of a mist using said composition under pressure and by gravity on the battery.